can't you just promise to give him blow jobs every week if he quits his "studying" and then go back to being happy and celebrating christmas?
If that doesn't work, how about finding a religion that you find compatible for BOTH of you as a family and ask him to join you in a non-denominational church.
Good luck, my husband has no affiliations with JW's and I told him right up front, if he ever considered it, plan on losing half of everything because i would divorce him. LOL.